Effect of blending two fiber-grade polypropylenes with different molecular weight distributions on the physical and structural properties of melt-spun filament yarns

摘要

In this study, the structural and physical properties of polypropylene fibers produced from the blending of two types of polymers having similar melt flow index but different molecular weight distributions (MWD) were investigated. Polypropylene with broad MWD (V30S grade) was blended with polypropylene with narrow MWD (511P grade) in various fractions (from 0% to 100%) to produce melt-spun filaments. Although the fraction of 511P in blends is higher than 25%, the blending is effective. Increasing the fraction of 511P in the blend increases tenacity and decreases breaking elongation. Mechanical properties of drawn yarns show the same trend as those of as-spun yams with the blend composition. For as-spun yarns, addition of 10% of 511P polymer increases birefringence in comparison with the V30S yarn. There is little or no effect of blend composition on the development of crystallinity. Drawing increased the birefringence and crystallinity of as-spun filament yarns, but the values of increase are different for the samples.